I advise you not to use the Betwonat-N cream on the foreskin of the penis. Foreskin retracting problem affects many males and therefore, you need to consult with a doctor for proper evaluation and treatment. The white substance underneath the foreskin might be smegma, but this can be treated with good personal hygiene practices. Hence, you should see a urologist for a follow-up evaluation and develop a detailed treatment strategy.